Two attributes of urban sprawl are an increase in impervious surface area and the urban heat island effect. As a result, forests and grasslands are being replaced with impervious surfaces such as buildings and parking lots, which cause an increase in storm water runoff. In addition, hard surfaces absorb and hold heat longer than green spaces, therefore causing an increase in the temperature of the surrounding atmosphere. Consequently, air conditioning use increases in communities and so do energy costs. Green roofs are a possible remedy to these problems; however, many variables determine whether a green roof system is successful. The research hypothesis for this project is that different growth media, plant species, and fertilizer selection will have an impact on green roof performance in the Midwest United States. Overall green roof performance was evaluated by percent roof coverage by plants. Four growth media Arkalite, Hadite, Pumice and Lava with a depth of four inches were evaluated. The Sedum species evaluated were S. sexangulare, S. spurium and S. kamtschaticum. Three fertilizer treatments, Osmocote, Nutricote and Isobutylidene diurea (IBDU) were evaluated. The above characteristics were evaluated during the 2007 and 2008 growing seasons and also in 2014, seven years after the experiment was started. I found that growth media, species and fertilizer selection had an impact on percent roof coverage.
At the end of the second growing season (2008) percent roof coverage for green roof blocks planted with Sedum spurium (58.3%) was greater than green roof blocks planted with other Sedum species measured. Plants treated with Osmocote fertilizer showed the greatest percent roof coverage throughout the first and second growing seasons (80.8%). Plants grown in Pumice growth media showed the highest percent roof coverage during the first growing season (52.3%), but plants grown in Lava growth media showed the highest percent roof coverage at the end of the second growing season (55.4%).
In 2014 there were no significant differences between fertilizer treatments. Plants grown in the Lava and Pumice growth media showed statistically similar percent roof coverage results in 2014 (8.6% and 8.3% respectively). Green roof blocks planted with S. spurium (7.7%) also showed the greatest amount of percent roof coverage in 2014, seven years after the experiment began. However, it was observed that S. spurium was not actually present in those blocks. S. album, from another green roof project, had established in those blocks.
My results support my hypothesis that different growth media, plant species, and fertilizer selection will have an impact on green roof performance in the Midwest United States. In addition, the low percent coverage results taken in 2014 showed that maintenance, such as fertilization and weed removal must be performed in order to maintain a sustainable green roof.
|Commitee:||Lin, Zhi-Qing, Morgan, Susan|
|School:||Southern Illinois University at Edwardsville|
|School Location:||United States -- Illinois|
|Source:||MAI 54/05M(E), Masters Abstracts International|
|Subjects:||Environmental management, Environmental science|
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